Flexible bushing and mold stool for cast tubular ingots



Jan. 29, 1957 B. BROWNSTEIN 2,

FLEXIBLE BUSHING AND MOLD STOOL FOR CAST TUBULAR INGOTS Filed Nov. 8. 1954 3 Sheets-Sheet l "ENTOR. Ben 0min wnsrein Mumm /W10.

HIS A7 ORNEYS Jan. 29, 1957 B. BROWNSTEIN 2,779,676

FLEXIBLE BUSHING AND MOLD STOOL FOR CAST TUBULAR INGOTS Filed NOV. 8, 1954 3 Sheets-Sheet 2 Fig. 2

INVENTOR. Ben amin Brownsle/n BY m wm Jan. 29, 1957 B. BROWNSTEIN 2,779,676

FLEXIBLE BUSHING AND MOLD STOOL FOR CAST TUBULAR INGOTS Filed Nov. 8, 1954 i 3 Sheets-Sheet 3 Fig. 6

INVENT Benjamin Brawn If) HIS A7 ORNEYS .tion. tendency of the shrinking ingot upon solidification to grip FLEXIBLE uusnmo AND MULD STOOL FDR CAST TUBULAR INGOTS This invention relates to a method and apparatus for forming a tubular ingot and particularly for casting a metal tubular ingot and later rolling the ingot into a seamless tube, pipe, hollow shafting, and the like.

In my prior patent, No. 2,616,137, which issued November 4, 1952, I have disclosed and claimed a mold and core for casting a tubular ingot wherein the surface of the bore of the resulting ingot is clean and smooth and free from such common defects as shrinkage cracks,

United Sees Patent blow holes, sand holes, fused sand, and the like which make the ingot unfit for rolling into a tube or pipe. I accomplish this, as described in my cited patent, by using a flexible core which is easily stripped from the bore of the ingot following solidification thereof and removed from the mold along with a solid backing metal core or cone which centers the flexible core in the mold.

While this apparatus performs the indicated functions very satisfactorily, experience has shown that a clear, smooth surface of an ingot bore oxidizes and scales, par ticularly when the ingot is subjected to the usual sequence of heating followed by cooling. This is very commonly met in practice when, for example, the ingot is heated in a soaking pit followed by removal from the pit and preparation for rolling in a continuous rolling mill. As is well known in the art, such scaling of an ingot bore is very objectionable and constitutes a serious problem.

I have now developed a mold and core for casting an ingot which not only retains the advantages of the apparatus disclosed in my Patent No. 2,616,137, but provides additional advantages. More particularly, my present invention provides a clean and smooth bore, completely avoids oxidation and scaling of the ingot bore, and more over facilitates any subsequent rolling or similar opera- To realize this, I take advantage of the natural the core utilized to impart the tubular formation. Previous attempts have been made to avoid or diminish such action, because a core such as an iron core becomes distorted by the shrinkage and is also gripped so tena- 'ciously by the shrinking metal that it is virtually impossible to separate the core from the cooled ingot. Accordingly, development has always, to my knowledge,

been in the other direction, namely, to minimize or prevent the ingot frorn gripping the core and to facilitate separation of the core from the ingot.

In the preferred form of my present invention, 1 use a flexible or yieldable centering cone or core as disclosed in my cited patent and an additional protective liner concentric with the flexible core. The protective liner, or what I may also term a flexible bushing, is composed of material resistant to heat, such as asbestos. The core and bushing are suitably positioned within a mold and the casting liquid, such as a liquid metal, poured therein. As the ingot shrinks and solidifies, it firmly grips the flexible bushing. Thereafter, the flexible core is removed from the mold and the bushing or liner remains behind, adhered to the bore of the ingot. The bushing protects the bore from oxidizing and scaling regardless of any 2,779,676 Fatented Jan. 29, 1957 subsequent heating and cooling. Moreover, when the ingot is eventually rolled over a supporting member such as a mandrel, the flexible bushing functions as a lubricant to facilitate greatly the rolling operation and prolong the useful life of the mandrel. t

A preferred form of my casting apparatus is illustrated by the accompanying drawings wherein:

Figure 1 is a plan view of the mold and core assembled for a casting operation;

Figure 2 is a vertical longitudinal section of Figure 1 on the line Ill-11;

Figures 3 and 4 are sections of Figure 2 on the lines III-4H and lV-IV, respectively;

Figure 5 is a partial, vertical, longitudinal section similar to Figure 2 showing a modification of the protective liner;

Figure 6 is a vertical longitudinal section of a cast ingot after removal from the mold illustrating the adhered protective liner; and

Figure 7 is a section of Figure 6 on the line VII-VII.

Referring to the drawings, my apparatus includes a stool ltl having a raised portion 11 provided with a further raised portion Ha. Raised portion 11 has a beveled periphery 12, and raised portion Ila has a centering socket 13 and an opening 14 extending from the socket through the floor of the stool. A centering ring 15 projects upwardly from the edge of the raised portion 11a and is substantially concentric with the centering socket 13.

A cylindrical mold 316 has a flanged lower end 17 which includes an outwardly beveled portion 18. The latter is complementary with the beveled periphery 12 of the mold stool so that the mold may be seated on the stool as shown. The upper end of the mold has an annular recess 19 which extends around the inside of the mold and is provided with an outwardly sloping wall 26.

1 preferably use the flexible core of my Patent No. 2,616,137 with my present improvement since each contributes to the other to provide an excellent casting as hereinafter described. In the embodiment shown, a flex ible core or cone generally shown at 21 is adapted for easy insertion and withdrawal with respect to the mold 16 and for this purpose'is tapered inwardly toward one end. This end has a pin 22 which makes a sliding fit in the bore of a centering sleeve 23 placed in the centering socket 113. A nut 57 screws onto the end of pin 22 and is adapted to pass through the opening 14. The upper end of the core 21 also has a pin 24 for centering purposes as hereinafter described.

The core 21 is made flexible, as that term is used herein, by an asbestos jacket which fits about a solid internal portion of the core. The jacket includes a conical tube 54, composed of plain and corrugated asbestos paper, which is wrapped around the solid internal portion of the core throughout its entire length. Around the conical tube 54, two or more layers of rope of an insulating, heat resisting fiber, such as asbestos, are wound. These ropes are wound in a spiral around the asbestos paper tube with the spirals of the different layers crossing one another. The spiral wound layers of asbestos rope are cemented together and to the asbestos conical tube with asbestos cement 56 which completely fills the spaces between the convolutions of the rope. Asbestos cement is also applied over the entire outer layer of the asbestos rope to provide a smooth, tapering outer surface for the core 21.

A flexible bushing 25 in substantially the form of a truncated cone which conforms with the taper of the flexible core 21 encloses the core preferably throughout the area which is exposed to the liquid metal from which the ingot is cast. The flexible bushing must withstand high temperatures, such as the temperature of the casting operation, and for this purpose may advantageously be corn-posed of mineral fibers such as asbestos fibers. The

bushing may take many forms, but the preferred form comprises at least one layer 26 of a corrugated asbestos sheet 26a which is contiguous to the flexible core 21 and arranged with the corrugations extending lengthwise of the core, a second layer 27 of asbestos overlying the first layer which may be preformed from bonded asbestos fibers, and a binder 28 such as asbestos cement which joins the two layers together. A chief advantage of this construction is that the corrugations of layer 26 are well adapted to be compressed under the force of the shrinking, cooling ingot. This compressibility of the corrugations aids in preventing shrinkage strains and, more importantly, diminishes any tendency toward adhesion between the layer 26 and the outer layer of: the flexible core 21 which might be introduced by the shrinking action. On the other hand, layer 27 is firmly gripped by the solidifying ingot. Consequently, the core 21 is easily separated from the bushing 25 and particularly layer 26 after the ingot has finally solidified, while, contrariwise, the ingot tenaciously holds layer 27. In particular, the use of a flexible core is advantageous here because of the relatively low sliding friction between layer 26 and the asbestos rope 55 and cement 56.

Layer 27 of the bushing 25 preferably has a lower flange 29 which extends to the centering ring and aids in sealing the bottom of the mold as hereinafter described. Layer 27 may also have an upper flange 36 to provide a seat 31. It is not necessary to use the upper flange 3t} with some metals which have such high shrinkage rates that the bushing is most firmly grasped without the use of end flanges on the flexible bushing. in such cases, the upper end of the bushing may be as shown by the reference numeral 27a in Figure 5.

Yoke means is used to position the upper end of the core 21 relative to the mold 16. As the term is used herein, the yoke means includes a cylindrical sleeve 32 comprising two sections 32a and 32b. The two sections are secured together by bolts 33 and nuts 34, the bolts passing through openings in aligned lugs 35 which extend from the sections. As mentioned in my prior Patent No. 2,616,137, which is hereby incorporated by reference, the sleeve 32 need not necessarily be made in two sections. The sections form an upstanding collar 36 which snugly fits around the pin 24 and provide an internal hollow chamber 37. At the bottom of the sleeve 32 there is a flange 38 terminating in a downwardly directed ring 39. If the embodiment of Figure 5 is used, the ring 39 may be omitted. The flange 38 and ring 39 seat against the top of the liner 25 and the flange Bil, respectively. A

centering ring 40 is shaped to seat in the annular recess 19 and.- is joined by connecting arms 41 to a smaller centering ring 42 which fits snugly about the collar 36. An eye 43 screws into a threaded opening in the pin 24.

In practice, with the apparatus disassembled, a layer of asbestos powder 44 is spread over the bottom of the centering socket 13 to act as a heat insulator. The wall of the socket 113 is then coated with graphite as indicated at 45 to lubricate the entrance of the centering sleeve 23 which is next inserted into the socket. The flexible bushing is now centered over the mold stool by engaging the flange 29 against the centering ring 15 as illustrated in Figure 2. The flexible core 21 is next inserted into the mold and more particularly into the liner 25. When the pin 22 'comes to rest within the bore of the centering sleeve 23,

the core 21 seats against the sleeve, and the flexible bushing 25 completely covers the flexible core from the raised portion 11a to a point above the top of the ingot to be cast.

In order to make a tight liquid joint between't'he bottom end Of-the bushing and the stool, an annular area around the centering ring .15 is filled with asbestos cement 46. Preferably, the latteris made to taper and align with the slope of the flange indicated at 47. The resulting asbestos 'fillet provides a'tight'joint between the asbestos flange 29 andthe moldstool "10. This prevents hot molten-metal from penetrating to the bottom part of the flange. The bevel 47 of the flange 29 directs the first hot molten metal as it is poured into the mold to the floor of the mold stool. This prevents the metal from sticking to the top of the flange and provides an even flow distribution of the metal over the floor of the mold.

Asbestos powder is applied on the raised portion 11 as at 48 and the mold 16 then placed around the flexible core and bushing and centered over the stool by the mating beveled surfaces 12 and 18. The sections 32a and 321) are next bolted in place at the top of the core and around the pin 24. Asbestos powder may also be applied to the wall 20 for insulating purposes as indicated at 49. The centering rings 40 and 42 are finally fitted into the recess 19 and around the collar 36, respectively. This arrangement places the flexible core 21 in the exact center of the mold 16.

The pouring of the hot molten metal is performed in the usual manner. As it cools, the casting shrinks and firmly grips the bushing 25 with an airtight seal between the outer surface of layer 27 and the surface of the ingot bore. As mentioned, the folds of the corrugated sheet 26a which are contiguous to the flexible core 21 are well suited to yielding under the resulting compressive forces so that the adhesion between the ingot and bushing 25 is many times greater than any adhesion created between the bushing and the outer surface of the core 21. Consequently, when the hook of a crane engages the eye 43 (which may be applied at any time), whatever adhesive force exists between the contacting asbestos surfaces of the core and the bushing as a result of the shrinkage of the ingot is broken in preference to the much stronger adhesive force existing between the ingot and the flexible bushing. As a result, the flexible core 21 is readily removed alone.

As the center of the core 31 the not :77 contacts the centering sleeve 23. This action effects the separation between the flexible bushing 25 and the asbestos rope 55 and cement 56 as just described. The center of the core 21 also strikes the underside of the sleeve 32 and thereby lifts as well the described yoke means. The mold is then stripped from the ingot in a. conventional way as by use of ears 50 to provide casting as shown in Figure 6 in which an ingot 51 still has the flexible bushing 25 adhered to its bore 52. The bore is not only smooth as realized principally by the flexible core, but protected against oxidation and subsequent scaling by the adhered flexible bushing.

It is especially emphasized that by means of the raised portion 11a, the bottom edge of the bushing 25 is ele vated somewhat from the bottom of the ingot, as illustrated in Figure 6. Accordingly, the ingot can be moved about and set down as desired as on a hearth floor without crushing the liner or otherwise breaking away the protective layers and destroying the airtight seal by which the bore is shielded against oxidation and scaling.

The ingot may now be heated preparatory to a rolling operation without destroying the liner or interfering with its function. it is within the contemplation of the method of my invention to roll the ingot with the liner still a dhercd. The rolling may be accomplished by conventional rolling mills inchiding the use of a mandrel to support the tubular ingot during such operation. For example, a continuous rolling mili and mandrel bar such as are disclosed in my prior patents, Nos. 2,140,414 and 2,025,- 439, may be used. At this time the flexible bushing 25 performs still another function, namely, that of reducing the frictional resistance between the bore of the hot tubular ingot, tube, or pipe and the surface of the mandrel. This, in turn, allows a higher rolling speed and prolongs the useful life of the mandrel. When asbestos is used as the mineral fibers, the asbestos is crushed and pulverized into a fine powder during the rolling operation by the When the finished tube or pipe emerges from the last roll pass,

there remains only a fine asbestos powder in the bore of the finished tube which is easily disposed of as by blowing.

While the foregoing disclosure describes a presently preferred embodiment and a modification thereof, it is understood that the invention may be practiced in still other forms Within the scope of the following claim.

I claim:

in a mold for casting a tubular ingot, the combination of a solid core, a tapered protective linear enclosing the solid core throughout the area, exposed to metal during solidfication of an ingot cast in the mold, and a mold stool for supporting the core and protective liner having a bushing engaging portion which is upwardly offset above the level of the bottom of the mold cavity, said protective liner comprising an inner jacket adjacent the core and an outer flexible bushing thereabout having an end supported upon said stool portion so as to be held in an upwardly ofiset position above the level of the bottom of the described ingot whereby, upon shrinkage and solidfication thereof, said ingot grips the outer flexible bushing whereupon the solid core and jacket may be withdrawn with the bushing left remaining in its upwardly offset position protecting the bore of the resulting ingot.

References Cited in the file of this patent UNITED STATES PATENTS 1,119,348 Robinson Sept. 15, 1914 1,912,965 Brownstein June 6, 1933 1,938,257 Jones Dec. 5, 1933 2,107,943 Hopkins Feb. 8, 1938 2,438,405 Kinnear Mar. 23, 1948 2,489,280 Flora et al Nov. 29, 1949 2,616,137 Brownstein Nov. 4, 1952 

